1. Field of the Invention
The invention relates to a process for the dehydration of peat. In peat extraction and processing reduction of the high water content of the peat is an essential prerequisite for processing. For the dehydration of peat almost exclusively natural air-drying has been used so far which is time-consuming and expensive and dependent on the weather. When being used as fuel, had to be added to the peat only partially dried in order to make combustion possible.
The invention is designed to dry peat in a way that the peat is dried by machine so as to facilitate combustion without additional firing or any kind of processing, for example, with manure, into briquettes for burning, into peat coke and the like. In order to solve this problem the invention consists essentially in the peat being supplied to a centrifuge capable of being closed so that it is pressure tight and being pressurized by saturated steam at a pressure of 2 to 35 bar, preferably 5 to 20 bar, while being centrifuged.
2. Description of the Related Art
Using saturated steam for drying organic substances is already known in connection with coals, reference being made in particular to the process according to Flei.beta.ner. The adsorption of water by coal differs considerably from the adsorption of water by peat and thus the technology developed for coal does not seem to be immediately applicable to peat. In connection with drying coals it has been further proposed by the Austrian Pat. Nos. 366 090, 366 405 and the 369 423 to use centrifuges in a successive drying step which centrifuges were pressurized by steam. The drying procedure of brown coals in a centrifuge by means of superheated steam subsequent to Flei.beta.ner-drying, which procedure is known from the Austrian Pat. No. 366 090, is not applicable to the drying of peat in the first step in view of the use of superheated steam, as peat has other physico-chemical properties than brown coal. In tests of comparison it has been found that by combining the drying procedure for brown coals using centrifuges, which procedure for successive drying steps is known from the Austrian Pat. Nos. 366 405 and 369 423, with saturated steam an unexpected dehydration effect which exceeds by far the summation effect in drying peat in the first drying step was achieved. While in treating black peat and white peat with saturated steam in a pressure range of 2 to 10 bar reduction of the water content in the range of 30 to 35% was achievable, reduction of the water content of more than 80% could be achieved by using centrifugal force simultaneously. The effect of dehydration essentially being increased by using saturated steam at the same time is presumably due to several factors favourable to dehydration. For one thing the temperature of treatment of the peat is increased by using saturated steam in the centrifugal field on account of the immediate discharge of the condensate and of the water liberated from the peat by which desorption of the water from the peat is favoured. At the same time the viscosity of the water being reduced, the separating effect is positively influenced in the system peat-water. Finally the compaction and/or compression of the peak cake occurring on account of the centrifugal forces causes additional water contained in the peat to be squeezed out.